Systems and methods for motion capture

ABSTRACT

Embodiments of the disclosure provide systems and methods for motion capture to generate content (e.g., motion pictures, television programming, videos, etc.). An actor or other performing being can have multiple markers on his or her face that are essentially invisible to the human eye, but that can be clearly captured by camera systems of the present disclosure. Embodiments can capture the performance using two different camera systems, each of which can observe the same performance but capture different images of that performance. For instance, a first camera system can capture the performance within a first light wavelength spectrum (e.g., visible light spectrum), and a second camera system can simultaneously capture the performance in a second light wavelength spectrum different from the first spectrum (e.g., invisible light spectrum such as the IR light spectrum). The images captured by the first and second camera systems can be combined to generate content.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a non-provisional application of and claimsthe benefit and priority under 35 U.S.C. 119(e) of U.S. ProvisionalApplication No. 62/575,157, filed Oct. 20, 2017 entitled “SYSTEM FORMOTION CAPTURE,” the entire contents of which are incorporated herein byreference for all purposes.

Computer animation is the process of generating animated images ofobjects in a computer environment. In the film industry, computeranimation is often used to animate the natural movement of humans forcreating realistic characters in a film that have humanoid features andmannerisms. This type of animation is known in the film industry asmotion-capture or performance capture. To capture the natural movementsof a human, an actor is equipped with a number of markers, and a numberof cameras track the positions of the markers in space as the actormoves. This technique allows the actor's movements and expressions to becaptured, and the captured movements and expressions can then bemanipulated in a digital environment to produce content, e.g., footagefor a motion picture.

Such motion capture systems however have shortcomings. For instance,some such systems may include additional equipment and markers thatinterfere with the performance of the actor. Accordingly, improvedsystems and methods for motion capture are desired.

SUMMARY

Embodiments provide systems and methods for motion capture to generatecontent (e.g., motion pictures, television programming, videos, etc.).In some embodiments, an actor or other performing being can havemultiple markers on his or her face that are essentially invisible tothe human eye, but that can be clearly captured by camera systems of thepresent disclosure. Embodiments of the disclosure can capture theperformance using two different camera systems, each of which canobserve the same performance but capture different images of thatperformance.

For instance, a first camera system can capture the performance within afirst light wavelength spectrum (e.g., visible light spectrum), and asecond camera system can simultaneously capture the performance in asecond light wavelength spectrum different from the first spectrum(e.g., invisible light spectrum such as the IR light spectrum). Theimages captured by the first and second camera systems can be combinedto generate content, such as animated content. Because the markers areinvisible to the first camera system but clearly visible to the secondcamera system, images captured by the first camera system may not needto be significantly edited to remove any markers on the actor's face andcan be used for various content production activities, such asgenerating movement of a digital or animated character. And, imagescaptured by the second camera system can be used to position the head ofan actor within a set or stage. Thus, the images can be used directlyfor generating content without needing to capture two separateperformances.

In some embodiments, the first and second camera systems can bestandalone cameras or mounted on a movable rig. Thus, these systemseliminate the need for head-mounted cameras for the motion capture of anactor's face. Eliminating the need for head-mounted cameras minimizesactor discomfort and improves actor performance and satisfaction.

In some embodiments, a computer-implemented method of capturing motionwith a motion capture system includes emitting first light atwavelengths within a first spectrum towards an actor in a performancearea, capturing a first plurality of images of a performance using afirst set of one or more cameras operable to capture the first light atwavelengths in the first spectrum, the first plurality of imagesrepresenting captured emitted first light that has been reflected off ofat least one marker applied to the face of the actor, identifyinglocations of at least one marker applied to the face of the actor byanalyzing at least some of the first plurality of images captured by atleast one camera from the first set of one or more cameras, generatingposition and motion data for a digital character based on the identifiedlocations of the at least one marker applied to the face of the actor,capturing a second plurality of images of the performance using a secondset of one or more cameras operable to capture second light atwavelengths in a second spectrum different from the first spectrum, thesecond plurality of images representing at least a portion of a body ofthe actor and the set surrounding the actor, and generating contentbased on the generated position and motion data for the digitalcharacter and the second plurality of images.

In some additional embodiments, a computer product including anon-transitory computer readable medium storing instructions that whenexecuted control a device including one or more processors. Theinstructions include emitting light at wavelengths within a firstspectrum towards an actor in a performance area, capturing a firstplurality of images of a performance using a first set of one or morecameras operable to capture first light at wavelengths in the firstspectrum, the first plurality of images representing captured emittedfirst light that has been reflected off of at least one marker appliedto the face of the actor, identifying locations of at least one markerapplied to the face of the actor by analyzing at least some of the firstplurality of images captured by at least one camera from the first setof one or more cameras, generating position and motion data for adigital character based on the identified locations of the at least onemarker applied to the face of the actor, capturing a second plurality ofimages of the performance using a second set of one or more camerasoperable to capture second light at wavelengths in a second spectrumdifferent from the first spectrum, the second plurality of imagesrepresenting at least a portion of a body of the actor and theperformance area, and generating content based on the generated positionand motion data for the digital character and the second plurality ofimages.

In certain embodiments, a computer system for a motion capture systemincludes one or more processors and memory containing code forinstructing the one or more processors to: emit light at wavelengthswithin a first spectrum towards an actor in a performance area, capturea first plurality of images of a performance using a first set of one ormore cameras operable to capture light at wavelengths in the firstspectrum, the first plurality of images representing captured emittedlight that has been reflected off of at least one marker applied to theface of the actor, identify locations of at least one marker applied tothe face of the actor by analyzing at least some of the first pluralityof images captured by at least one camera from the first set of one ormore cameras, generate position and motion data for a digital characterbased on the identified locations of the at least one marker applied tothe face of the actor, capture a second plurality of images of theperformance using a second set of one or more cameras operable tocapture light at wavelengths in a second spectrum different from thefirst spectrum, the second plurality of images representing at least aportion of a body of the actor and the performance area, and generatecontent based on the generated position and motion data for the digitalcharacter and the second plurality of images.

In some embodiments, a system for motion capture includes a first set ofone or more cameras operable to capture first light at wavelengths in afirst spectrum, the first set of one or more cameras positioned around aperformance area to capture a first series of images of an actor duringa performance by the actor in the performance area, one or more lightsources configured to emit first light at wavelengths in the firstspectrum to illuminate at least a portion of the actor during theperformance with the first light, and a second set of one or morecameras operable to capture light at wavelengths in a second spectrumdifferent from the first spectrum, the second set of one or more cameraspositioned around the performance area to capture a second series ofimages of the actor during the performance simultaneously with the firstset of one or more cameras so that the first and second set of one ormore cameras are configured to capture images of the performance at thesame time, but the content of the first series of images are differentfrom the second series of images due to the different spectrums of lightin which each set of one or more cameras operates.

In some additional embodiments, a system for motion capture includes aplurality of wheels, a frame mounted on the plurality of wheels, theplurality of wheels configured to allow the frame to be carted todifferent positions around a performance area, a first camera mounted tothe frame and operable to capture first light at wavelengths in a firstspectrum, and second and third cameras mounted to the frame at specificlocations relative to the first camera, the second and third camerasoperable to capture second light at wavelengths in a second spectrumdifferent from the first spectrum, the first, second, and third camerasbeing configured to simultaneously capture images of an actor in theperformance area during a performance.

In certain embodiments, a system for motion capture includes a set ofone or more witness cameras positioned on stands that holds the set ofone or more witness cameras in an elevated positioned around aperformance area to capture a first series of images of an actor duringa performance by the actor in the performance area, the set of one ormore witness cameras being operable to capture first light atwavelengths in a first spectrum, one or more light sources positionedaround the performance area and configured to emit first light atwavelengths in the first spectrum to illuminate at least a portion ofthe actor during the performance with the first light, and a takingcamera operable to capture light at wavelengths in a second spectrumdifferent from the first spectrum, the taking camera positioned aroundthe performance area to capture a second series of images of the actorduring the performance simultaneously with the first set of one or morecameras so that the taking camera and the set of one or more witnesscameras are configured to capture images of the performance at the sametime, but the content of the first series of images are different fromthe second series of images due to the different spectrums of light inwhich the cameras operate.

A better understanding of the nature and advantages of embodiments ofthe present disclosure may be gained with reference to the followingdetailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary motion capture system,according to some embodiments of the present disclosure.

FIG. 2 is a simplified diagram of an exemplary motion capture systemconfigured with a taking camera and stationary witness cameras,according to some embodiments of the present disclosure.

FIG. 3 is a simplified diagram of an exemplary motion capture systemconfigured with a taking camera and two witness cameras, all of whichare mounted on a movable rig, according to some embodiments of thepresent disclosure.

FIG. 4 is a detailed, front-facing, perspective view of a motion capturesystem configured as a movable rig, according to some embodiments of thepresent disclosure.

FIGS. 5A-5B are simplified illustrations of only the front ends of ataking camera and witness cameras in different camera arrangements,according to some embodiments of the present disclosure.

FIG. 6A is a simplified diagram of an exemplary configuration of amotion capture system where an actor is positioned close to the system,according to some embodiments of the present disclosure.

FIG. 6B is a simplified diagram of an exemplary configuration of amotion capture system where an actor is positioned far away from thesystem, according to some embodiments of the present disclosure.

FIG. 7 is a simplified illustration of exemplary positions for gel-basedmarkers that enable motion capture of the skull of an actor during aperformance, according to some embodiments of the present disclosure.

FIG. 8 is a flow diagram of a method for performing motion capture witha motion capture system, according to some embodiments of the presentdisclosure.

FIG. 9 is a simplified block diagram of system for creating computergraphics imagery (CGI) and computer-aided animation that may implementor incorporate various embodiments in accordance with the disclosure.

FIG. 10 is a block diagram of an exemplary computer system, according tosome embodiments of the present disclosure.

The present invention will now be described in detail with reference tocertain embodiments thereof as illustrated in the above-referenceddrawings. In the following description, numerous specific details areset forth in order to provide a thorough understanding of the presentinvention. It will be apparent, however, to one skilled in the art, thatthe present invention may be practiced without some or all of thesespecific details. In other instances, well known details have not beendescribed in detail in order not to unnecessarily obscure the presentinvention.

DETAILED DESCRIPTION

Embodiments of the present disclosure describe a motion capture systemthat includes two types of cameras for generating content. The firsttype of camera can be a taking camera configured to capture images of anactor in the visible light wavelength spectrum. The second type ofcamera can be a witness camera configured to capture images of markerson the actor in an invisible light wavelength spectrum, e.g., infrared(IR) light wavelength spectrum. In some embodiments, the markers on theactor are designed to reflect light only in the IR light wavelengthspectrum. Thus, the markers may not be visible to the taking camera, butclearly visible to the witness camera(s). It is to be appreciated thatthe words “visible” and “invisible” used herein are to be interpreted inrelation to what is detectable by the naked eye. By being configured tocapture light in different spectrums, the taking camera and the one ormore witness cameras can simultaneously capture different aspects of ascene based on their respective light wavelengths, thereby eliminatingthe need to capture two separate performances of the same scene togenerate content.

In some embodiments, the witness camera(s) are standalone cameras thatare stationary and positioned to capture markers on an actor from onepoint of view. Each witness camera can be positioned in differentlocations around a set so that the markers on the actor can be capturedfrom different angles. The taking camera, on the other hand, can be astandalone camera like the witness cameras, but it may not bestationary. For instance, the taking camera can move around the setwhile the witness camera(s) are stationary. In some additionalembodiments, the motion capturing system can be mounted on the samechassis of a single, movable rig. As an example, a motion capturingsystem can include a taking camera and two witness cameras laterallypositioned on opposite sides of the taking camera. All three cameras canbe pointing in the same general direction such that all three camerascan capture the same scene but at different angles. By separating takingand witness cameras from an actor's head, the actor can be lessdistracted during takes and be more comfortable throughout the shoot.Furthermore, mounting the motion capturing system on the same rig allowsthe entire system to be easily moved around a set.

Details of such motion capture systems will be discussed in detailfurther herein.

I. Motion Capture System

FIG. 1 is a block diagram of an exemplary motion capture system 100,according to some embodiments of the present disclosure. Motion capturesystem 100 includes a taking camera 102 and one or more witness cameras104. Each of taking camera 102 and witness camera(s) 104 can be anysuitable image capturing device that can measure light and generate animage based on the measured light. In some embodiments, taking camera102 is a first type of camera that can measure light in the visiblelight wavelength spectrum, and witness camera(s) 104 is a second type ofcamera that can measure light in the invisible light wavelengthspectrum, where the visible and invisible light spectrums do notoverlap. For example, taking camera 102 can be an RGB camera that cangenerate images by measuring light at wavelengths between approximately390 to 700 nm, and witness camera(s) 104 can be two IR cameras that cangenerate images by measuring light at wavelengths between approximately701 nm to 1 mm. In some embodiments, the visible and invisible lightspectrums do not overlap so that taking camera 102 and witness camera(s)104 capture different images even though they may be focused onsubstantially the same object in the area of a set.

In some embodiments, motion capture system 100 includes taking cameralight sources 108 and witness camera light sources 110. Each lightsource can be designed to emit light between a wavelength spectrum thatmatches the wavelength spectrum of a corresponding camera so that atleast some light emitted from the light sources can be captured byrespective cameras in system 100 after being reflected off of surfacesof actor 106. For example, taking camera light sources 108 can emitvisible light 112 to illuminate actor 106. At least a portion 114 ofvisible light 112 can reflect off of actor 106 and be captured by takingcamera 102. Likewise, witness camera light sources 110 can emitinvisible light 116 to illuminate actor 106, and at least a portion 118of invisible light 116 can reflect off of actor 106 and be captured bytaking camera 102. In some embodiments, portion 114 of visible light 112is reflected off of the face, hair, head, neck, shoulders, or any otherbody part of actor 106, while portion 118 of invisible light 116 isreflected off of markers 120 on a face of actor 106. In certainembodiments such markers 120 can reflect invisible light but not visiblelight so that markers 120 are substantially undetectable by takingcamera 102. In other embodiments, such markers 120 can be relativelymore reflective of invisible light than visible light such that markers120 are substantially undetectable by taking camera 102.

Operation of motion capture system 100 can be better understood from anexemplary use case scenario. For example, during filming of a motionpicture, taking camera 102 can be used to capture the entire compositionof a set, e.g. actor 106 looking around at his surroundings in front ofa busy street in New York City. Taking camera light sources 108 areflood lights shining white, visible light that illuminates the scenewith visible light so that taking camera 102 can capture footage ofactor 106 as he or she looks around, as well as any extras walkingaround the busy street, any building facades around actor 106, and anycars that may pass by actor 106. Meanwhile, witness camera light sources110 are flood lights shining invisible, IR light that illuminates thescene with IR light so that witness cameras 104 can simultaneouslycapture footage of markers 120 on the face of actor 106. Markers 120 canbe configured as a retro-reflectors that can substantially reflect IRlight, as will be discussed further herein. Accordingly, markers 120 mayappear as bright dots in the images captured by witness cameras 104.

Because taking camera 102 may be unable to detect IR light, the imagescaptured taking camera 102 may not include portions 118 of reflected IRlight from markers 120. As a result, the images captured by takingcamera 102 may be used directly in an item of content and/or used todrive a digital replica of actor 106 based on a markerless motionsolving system. In some embodiments, markers 120 can be detectable inboth visible and invisible light spectrums. For instance, markers 120can be black dots that are detectable in both visible light and IRlight. In such instances, taking camera 102 and witness cameras 104 canboth capture the positions of markers 120, thereby enabling a morerobust triangulation of the face of actor 106 during the performance.

By having two types of cameras 102 and 104 and two respective lightsources 108 and 110, motion capture system 100 can effectively andefficiently capture two different motion picture compositions with oneshoot, i.e., act of filming. Thus, motion capture system 100 enables thegeneration of content using a minimal number of performances by actor106. More specifically, actor 106 only needs to perform a singleperformance in order (1) to generate images directly usable for an itemof content and/or driving a digital character in a virtual environmentand (2) for accurately determining the location of a digital charactermapped to the head of actor 106 in a virtual environment.

Based on the images captured from taking camera 102 and witness cameras104, motion capture system 100 can determine the locations of variousparts of the head of actor 106 during a performance. In someembodiments, the captured images from taking camera 102 and witnesscameras 104 can be provided to a computer system 122, which can belocated at a remote location, such as in an editing studio, or it can bepositioned within the near vicinity of cameras 102 and 104. Computersystem 122 can be a special-purpose computer system, such as a contentgeneration system, that utilizes the captured images from taking camera102 and the locations of markers 120 of actor 106 captured by witnesscameras 104 to position a digital or virtual head corresponding to theactor's head in a virtual environment or set. The content generationsystem may then generate content (e.g., a film or TV programming) basedon the positioning. For example, continuing from the use case scenarioabove, computer system 122 can position a digital or virtual face on theactor's head to make him look different while the actor is lookingaround at his surroundings in front of the busy street in New York City.The images captured by taking camera 102 can be the actor's head, body,and his surroundings, while the images captured by witness cameras 104can be the positions of markers 120 relative to the actor's head, body,and his surroundings. Thus, the positions of markers 120 can be used toaccurately and realistically position the digital or virtual face on theactor's head during the performance. Details of computer system 122 isdiscussed in further detail herein with respect to FIGS. 9 and 10.

In some embodiments, taking camera 102 and witness cameras 104 in motioncapture system 100 can be configured in various different ways. Forinstance, taking camera 102 and witness cameras 104 can each bestandalone cameras where witness cameras 104 are stationary. In anotherexample, motion capture system 100 can be configured so that takingcamera 102 and witness cameras 104 are all mounted on a same rig so thatthe cameras form a single image capturing device. Each of theseembodiments will be discussed in detail further herein with respect toFIGS. 2-6B.

A. Stationary Witness Cameras

As mentioned above, a motion capture system can include tracking andwitness cameras where the tracking and witness cameras are standalonecameras, and where the witness cameras are also stationary. An exemplarymotion capture system with such a configuration is shown in FIG. 2.

FIG. 2 is a simplified diagram of an exemplary motion capture system 200configured with a taking camera 202 and stationary witness cameras 204a-d where stationary witness cameras 204 a-d are stationary, standalonecameras, according to some embodiments of the present disclosure. Eachwitness camera 204 a-d can be stationary in that they are not easilymovable once they are positioned in place and are not intended to bemoved during a performance by actor 206. For example, each witnesscamera 204 a-d can rest on stands that fix witness cameras 204 a-d inplace throughout an entire performance by actor 206. Although system 200includes four witness cameras 204 a-d, it is to be appreciated thatembodiments are not limited to such configurations and that otherembodiments can have more or less witness cameras.

Taking camera 202, on the other hand, does not have to be stationary andcan move around while actor 206 is performing. As an example, takingcamera 202 can be mounted on a rail and move between two locations tocapture a moving shot of actor 206 during his or her performance. Inanother example, taking camera 202 can move from point A to point B andthen to point C throughout a performance by actor 206. Taking camera 202is shown with dashed lines in positions B and C is to illustrate thatthere is one taking camera (instead of three) and that it can move todifferent positions around actor 206.

According to some embodiments of the present disclosure, taking camera202 operates to capture light in a first wavelength spectrum, andwitness cameras 204 a-d operate to capture light in a second wavelengthspectrum different from the first wavelength spectrum such that the twospectrums do not overlap. As an example, taking camera 202 can operateto capture visible light (i.e., light at wavelengths betweenapproximately 390 to 700 nm) and witness cameras 204 a-d can operate tocapture invisible light (i.e., IR light at wavelengths betweenapproximately 701 nm to 1 mm). To prevent overlap in the operablewavelengths of taking camera 202 and witness cameras 204 a-d, one ormore modifications can be implemented for each respective camera. As anexample, IR filters can be implemented in front of the taking lenses forwitness cameras 204 a-d to only allow IR light to pass through.Additionally, witness cameras 204 a-d can be implemented with an IRimage sensor that can detect IR light only, or witness cameras 204 a-dcan be implemented with an image sensor that does not have a coatingthat filters IR light so that IR light is allowed to be detected by theimage sensor. It is to be appreciated that any other modification toseparate the operating wavelength spectrums of taking camera 202 andwitness cameras 204 a-d without departing from the spirit and scope ofthe present disclosure can be envisioned in embodiments herein.

In certain embodiments, a plurality of light sources can project lightagainst actor 206 to enable and/or improve the quality of imagescaptured by taking camera 202 and witness cameras 204 a-d. For instance,motion capture system 200 can include taking camera light sources 208a-c and witness camera light sources 210 a-c. In some embodiments,taking camera light sources 208 a-c and witness camera light sources 210a-c can emit light in different wavelength spectrums that correspond tothe operating wavelengths of respective cameras for which they areconfigured to provide illumination. As an example, taking camera lightsources 208 a-c can emit visible light 212 and witness camera lightsources 210 a-c can emit IR light 214. It is to be appreciated that foroutdoor sets during the day, there may be enough ambient visible and IRlight from the sun such that taking camera light sources 208 a-c and/orwitness camera light sources 210 a-c may not be needed for taking camera202 and witness cameras 204 a-d to capture images of actor 206. Thus,taking camera light sources 208 a-c may be optional in motion capturesystem 200.

During filming while actor 206 is performing, portions of light 212 and214 emitted from light sources 208 a-c and 210 a-c (or from ambientvisible and IR light) can reflect back to cameras 202 and 204 a-d, whichcan then simultaneously capture images of actor 206 and/or the actor'ssurroundings. As an example, a portion 216 of visible light emitted fromone or both taking camera light sources 208 a and 208 c can be reflectedoff of a face, or the entire body, of actor 206 and be captured bytaking camera 202 in position B. In addition to portion 216, a portion218 of visible light can be reflected off of objects in the set aroundactor 206, such as a chair 220 (or, from the use case scenario above,building facades, passing cars, or any other type of object found on abusy street in New York City), and also be captured by taking camera 202in position B. According to some embodiments of the present disclosure,portions 222 and 224 of invisible light emitted from witness cameralight source 210 a can be reflected off a marker 226 on the face ofactor 206 and be captured, simultaneously with the capturing of visiblelight by taking camera 202, by respective witness cameras 204 a and 204b. As can be seen from FIG. 2, witness cameras 204 a and 204 b can bepositioned in different locations around the set and actor 206; thus,witness cameras 204 a and 204 b can view marker 226 from differentangles and distances. The captured images of marker 226 can be utilizedby a computer system, e.g., computer system 122 in FIG. 1, totriangulate the position of marker 226 in a three-dimensionalenvironment. The triangulated position of marker 226 can be combinedwith the footage captured by taking camera 202 to generate accuratedigital performances of actor 206 in the set or digital performances ofa digital character in a virtual environment. The same can be said forportions 221 and 223 of reflected IR light from marker 234, and portion228 of reflected visible light from the face of actor 206, when takingcamera 202 is at position C, or any other position around actor 206,e.g., position A.

It can be appreciated that implementing more witness cameras indifferent positions around actor 206 can more reliably capture themovement of actor 206. This is because when actor 206 is performing,some markers may be visible to some witness cameras but appear blockedto other witness cameras. For instance, as shown in FIG. 2, marker 226may be visible to witness cameras 204 a and 204 b, but appear blocked towitness cameras 204 c and 204 d. In other instances, some objects (e.g.,a boom mic, filming personnel, and the like) around the set mayunintentionally occlude the view of one or more witness cameras. Byhaving more witness cameras around actor 206, there is a greater chancethat there will be at least one or more witness cameras that can capturethe movement of marker 226 even though one or more witness cameras areoccluded. Furthermore, using a greater number of witness cameras canminimize the occurrence where a marker is not visible to any witnesscamera. In such situations, calculation of the position of marker 226may not be possible, or the calculation may be based on the capturedimages from taking camera 202, which may result in an inaccuratedetermination of the marker's position because of a lack of depthperception. In such embodiments, marker 226, and other markers visibleon the face of actor 206, can be visible to taking camera 202 andwitness cameras 204 a-d. For instance, marker 226 can be a black markerthat absorbs visible light and reflects IR light. That way, from theperspective of taking camera 202, marker 226 appears as a block dot; andfrom the perspective of witness cameras 204 a and 204 b, marker 226appears as a bright dot. In some other embodiments, however, marker 226can be visible to witness cameras 204 a-d but invisible to taking camera202, as will be discussed further herein with respect to FIG. 7.

By implementing two types of cameras, e.g., taking camera 202 andwitness cameras 204 a-d, that operate to capture light atnon-overlapping wavelength spectrums, motion capturing system 200 caneffectively and efficiently capture two different video footages withone shoot. Thus, motion capture system 200 enables the generation ofcontent using a minimal number of performances by actor 206. Morespecifically, actor 206 only needs to perform a single performance inorder (1) to generate images directly usable for an item of contentand/or driving a digital character in a virtual environment and (2) foraccurately determining the location of a digital character mapped to thehead of actor 206 in a virtual environment.

B. Non-Stationary Witness Cameras

As can be appreciated by the illustration of FIG. 2, motion capturesystem 200 includes several standalone components, e.g., taking camera202 and four witness cameras 204 a-d. If the director shooting actor 206in a set wants to change scenes and set locations, each of thestandalone components may need to be moved individually. To simplifythis process and enable motion capture system 200 to be more mobile andversatile, the taking camera and witness cameras can be mounted on asingle, movable structure so that witness cameras 204 a-d arenon-stationary, as discussed herein with respect to FIG. 3.

FIG. 3 is a simplified diagram of an exemplary motion capture system 300configured with a taking camera 302 and two witness cameras 304 a-bwhere taking camera 302 and stationary witness cameras 304 a-b aremounted on a movable rig 303, according to some embodiments of thepresent disclosure. Rig 303 with taking and witness cameras 302 and 304a-b is shown from the top-down perspective. Taking camera 302 andwitness cameras 304 a-b can be configured to be substantially similar totaking camera 202 and witness cameras 204 a-d in FIG. 2. Accordingly,details of taking camera 302 and 304 a-b can be referenced in thedisclosure of FIG. 2 and are not discussed herein for brevity.

As shown in FIG. 3, taking camera 302 and witness cameras 304 a-b can berigidly mounted on a single structure 305, according to some embodimentsof the present disclosure. Structure 305 can be a stiff frame that ispart of rig 303 and strong enough to support the weight of cameras 302and 304 a-b, such as a steel frame with bolting points for securingcameras 302 and 304 a-b. Additionally, rig 303 can include a set ofwheels 307 that enable rig 303, along with taking camera 302 and witnesscameras 304, to roll between different positions around actor 306, suchas between position A and position B. By being mounted on movable rig303, witness cameras 304 a-b are non-stationary, thereby significantlysimplifying the moving process of motion capture system 300, whether itbe for moving to different shot angles within a set, or for moving to acompletely new set at a different location.

In certain embodiments, motion capture system 300 can include aplurality of light sources for projecting light against actor 306. Forinstance, motion capture system 300 can include taking camera lightsources 308 a-b positioned to illuminate actor 306 from differentangles. Like taking camera light sources 208 a-c in motion capturesystem 200 of FIG. 2, taking camera light sources 308 a-b can beoptional standalone light sources. However, unlike witness camera lightsources 210 a-c in motion capture system 200, witness camera lightsources 310 a-b can each be a part of a respective witness camera 304a-b. Thus, witness cameras 304 a-b can not only capture invisible (IR)light, but they can also illuminate actor 306 with invisible light,thereby reducing the number of standalone components for a motioncapture system.

As an example, witness camera light source 310 a can be formed as partof, or attached to, a lens hood 311 a of witness camera 304 a. In someembodiments, witness camera light source 310 a is constructed as a ringof light emitters (e.g., light emitting diodes (LEDs)) positioned arounda circumference of the front end of lens hood 311 a. When constructed asa ring of light emitting diodes, witness camera light source 310 a canproject invisible (IR) light 314 at actor 306 from the exact angle atwhich witness camera 304 a perceives actor 306. Thus, invisible light314 cast upon actor 306 may not create any shadows when viewed from theposition of witness camera 304 a, thereby maximizing illuminationefficiency of actor 306 and the brightness of reflected light detectedby witness camera 304 a. It is to be appreciated that taking cameralight sources 308 a-b and witness camera light sources 310 a-b can besubstantially similar in function to taking camera light sources 208 a-cand witness camera light sources 210 a-b of motion capture system 200 inFIG. 2, and thus have the same function and purpose. i.e., providevisible and invisible light to improve the quality of images captured bytaking camera 302 and witness cameras 304 a-b. A better understanding ofthe structure and construction of such a motion capture system can beachieved with reference to FIG. 4

FIG. 4 is a detailed, front-facing, perspective view of a motion capturesystem 400 configured as a movable rig, such as motion capture system300 in FIG. 3, according to some embodiments of the present disclosure.For ease of discussion, components of motion capture system 400 thatcorrespond with components of motion capture system 300 are labeled withthe reference number used in FIG. 3.

As shown in FIG. 4, taking camera 302 and witness cameras 304 a-b aremounted on movable rig 303. In some embodiments, rig 303 can include ahead portion 402 coupled to a body portion 404. Head portion 402 canextend forward and be closer to a filming subject (e.g., an actor in aset) than body portion 404 and include a head frame 406 (of whichsupport structure 305 is a part) along with various electrical wires andother ancillary components for enabling the operation of cameras 302 and304 a-b. Body portion 404 can include a body frame 408 to which aplurality of wheels 307 can be mounted to enable movement of motioncapture system 400. In some embodiments, head frame 406 is coupled tobody frame 408 via nuts and bolts or by welding joints. In certainembodiments, head frame 406 and body frame 408 are part of a samemonolithic structure. Head frame 406 and body frame 408 together canform a chassis on which cameras 302 and 304 a-b are mounted.

According to some embodiments of the present disclosure, taking camera302 and witness cameras 304 a-b can be mounted on support structure 305so that taking camera 302, witness cameras 304 a-b, and supportstructure 305 together form a rigid composition of components that cantilt and turn together as a whole. In some embodiments, structure 305 isa support plate that has sufficient tensile strength to hold cameras 302and 304 a-b in a stable position above ground. Structure 305 can bendaround taking camera 302 to provide clearance space for taking camera302 while providing additional structural strength. In some embodiments,witness cameras 304 a-b can be mounted on laterally opposite sides oftaking camera 302 so that witness cameras 304 a-b and taking camera 302are substantially aligned to the same horizontal axis 401. It is to beappreciated, however, that embodiments are not limited to suchconfigurations, as will be discussed further herein with respect to FIG.6B.

As mentioned herein, witness cameras 304 a-b can be configured tocapture light only in the invisible (IR) wavelength spectrum. Thus, oneor more optical filters 410 a-b can be positioned in front of therespective lenses of witness cameras 304 a-b. That way, only IR lightcan pass through to witness cameras 304 a-b.

With reference back to FIG. 3, during image capture while actor 306 isperforming, portions of light 312 and 314 emitted from light sources 308a-b and 310 a-b can reflect back to cameras 302 and 304 a-d,respectively, which can then simultaneously capture images of actor 306and/or the actor's surroundings. As an example, a portion 316 of ambientlight or visible light emitted from taking camera light source 308 a canbe reflected off of a face, or the entire body, of actor 306 and becaptured by taking camera 302 in position A. In addition to portion 316,a portion 318 of visible light can be reflected off of objects in theset around actor 306, such as a chair 320 (or, from the use casescenario above, building facades, passing cars, or any other type ofobject found on a busy street in New York City), and also be captured bytaking camera 302 in position A. According to some embodiments of thepresent disclosure, portions 223 and 324 of invisible light emitted fromwitness camera light sources 310 a and 310 b, respectively, can bereflected off a marker 326 on the face of actor 306 and be captured,simultaneously with the capturing of visible light by taking camera 302,by respective witness cameras 304 a and 304 b.

As can be seen from FIG. 3, witness cameras 304 a and 304 b can bepositioned at laterally opposite sides of taking camera 302; thus,witness cameras 304 a and 304 b can view marker 326 from differentangles and distances. This information can be utilized by a computersystem, e.g., computer system 122 in FIG. 1, to triangulate the positionof marker 326 in a three-dimensional environment. The triangulatedposition of marker 326 can be combined with the footage captured bytaking camera 302 to generate accurate digital performancescorresponding to actor 306. The same can be said for portions 330 and332 of reflected IR light from marker 234, and portion 328 of reflectedvisible light from the face of actor 306, when taking camera 302 is atposition B, as shown in FIG. 3, or any other position around actor 306.By being mounted on laterally opposite sides of taking camera 302,witness cameras 304 a-b can be better positioned to track the movementsof markers on the face of actor 306 because of the natural symmetry of ahuman's face across a vertical axis. For instance, witness camera 304 acan better capture markers on the left side of actor's 306 face whilewitness camera 304 b can better capture markers on the right side ofactor's 306 face. And, when both cameras 304 a-b are utilized together,the accuracy of determining the position of markers on actor 306 bytriangulation can be increased.

It is to be noted that unlike motion capture system 200 in FIG. 2 wherewitness camera light sources 210 a-c are positioned around actor 206 toilluminate actor 206 from all angles, witness camera light sources 310a-b only illuminate actor 306 from the angles at which witness cameras304 a-b are positioned. In this case, it may not be necessary toilluminate actor 306 with invisible light from any other light source ata different position because such invisible light will not be utilized,or will have negligible utilization, by witness cameras 304 a-b. Tofurther increase the amount of reflected invisible light 314 emitted bywitness camera light sources 310 a-b, markers on the face of actor 306,including markers 326 and 334, can be configured as retroreflectivegel-based markers that reflect light back to its source with minimalscattering, as will be discussed further herein with respect to FIG. 7.Furthermore, to further differentiate the captured images by takingcamera 302 and witness cameras 304 a-b, the markers can be invisible totaking camera 302 but visible to witness cameras 304 a-b. That way,taking camera 302 may not capture markers 326 and 334 on actor 306during the performance so that the captured footage may not need to beedited to remove the presence of markers 326 and 334, which may often bethe case where such markers are visible to taking camera 302. This cansave time and cost associated with post processing of the capturedimages.

1. Camera Configurations

As mentioned herein with respect to FIGS. 3 and 4, witness cameras 304a-b can be mounted on laterally opposite sides of taking camera 302. Insome embodiments, witness cameras 304 a-b can be positioned at variousdistances away from taking camera 302 as discussed herein with respectto FIG. 5A. FIG. 5A is a simplified illustration 500 of only the frontends of taking camera 302 and witness cameras 304 to better illustratetheir positioning with respect to one another, according to someembodiments of the present disclosure. Additionally, the referencenumerals used in FIG. 3 are used in FIG. 5A for ease of understanding.

As shown in FIG. 5A, witness camera 304 a is positioned a distance D1away from a left side of taking camera 302 and witness camera 304 b ispositioned a distance D2 away from a right side of taking camera 302. Insome embodiments, D1 and D2 are the same distances such that witnesscamera 304 a is positioned the same distance away from taking camera 302as witness camera 304 b. In other embodiments, D1 and D2 can bedifferent. D1 and D2 can be increased and decreased depending ondistance to the actor and desired accuracy for triangulation. Forinstance, when the actor is positioned farther away, D1 and D2 may needto be increased to get more distinct captured images. If the distancesD1 and D2 were small and the actor was positioned far away, witnesscameras 304 a-b may essentially be capturing the same images given theirclose proximity to one another relative to their distance away from theactor, thereby decreasing the accuracy of triangulation. In someembodiments, distances D1 and D2 are each between six inches and twofeet.

Although embodiments herein have discussed motion capture systems withmovable rigs as having two witness cameras positioned on laterallyopposite sides of a taking camera, embodiments are not limited to suchconfigurations, and that any configuration with more or less than twocameras positioned in any location around the taking camera areenvisioned herein. FIG. 5B is a simplified illustration of an exemplarycamera arrangement 501, according to some embodiments of the presentdisclosure. Camera arrangement 501 can include taking camera 502surrounded by witness cameras 504 a-d. Witness cameras 504 a-b can bepositioned on laterally opposite sides of taking camera 502, whilewitness cameras 504 c-d can be positioned on vertically opposite ends oftaking camera 502, as shown in FIG. 5B. By having witness cameras 502c-d in addition to witness cameras 504 a-b, an additional pair ofwitness cameras can provide positioning information to increase theaccuracy of position determination of markers on an actor. Although FIG.5B illustrates camera arrangement 501 as having witness cameras 504 a-dpositioned laterally and vertically with respect to taking camera 502,embodiments are not limited to such configurations and thatconfigurations with any number of witness cameras positioned in anylocation around taking camera 502 are envisioned herein.

2. Angle of Orientation of Witness Cameras

In addition to being able to modify the distance between the takingcamera and each witness camera, motion capture systems with movable rigscan also modify the rotational orientation of each witness camera. Forinstance, witness cameras can be oriented in different angles forfilming subjects positioned at different distances away from the motioncapturing system. FIGS. 6A and 6B illustrate exemplary configurationsfor a motion capturing system where a filming subject is positioned atdifferent distances away from the motion capturing system, according tosome embodiments of the present disclosure. Specifically, FIG. 6A is asimplified diagram of an exemplary configuration 600 of motion capturesystem 300 of FIG. 3 where actor 306 is positioned close to system 300,and FIG. 6B is a simplified diagram of an exemplary configuration 601 ofmotion capture system 300 where actor 306 is positioned far away fromsystem 300.

In some embodiments, witness cameras 304 a-b can be rotated aroundrespective pivot points 602 a-b so that witness cameras 304 a-b can bepositioned at different angles with respect to support structure 305.For instance, as shown in FIG. 6A, when actor 306 is positioned close tosystem 300, witness cameras 304 a-b can each be pivoted aroundrespective pivot points 602 a-b and be oriented along respective centralaxes 604 a-b so that cameras 304 a-b are pointed at actor 306. In suchinstances, central axes 604 a-b can be oriented at respective angles 606a-b. On the other hand, when actor 306 is positioned far away fromsystem 300, as shown in FIG. 6B, witness cameras 304 a-b can be pivotedaround their respective pivot points 602 a-b so that their central axis604 a-b are oriented at respective angles 606A-b, which are greater thanangles 606 a-b. Angles 606 a-b and 606A-b may not exceed 90 degrees toensure that witness cameras 304 a-b can focus on actor 306. By enablingwitness cameras 304 a-b to rotate around a pivot point, motion capturesystem 300 can be better suited to capture motion when actor 306 ispositioned at various distances away from the motion capture system asthe actor may perform at different locations in a set.

In some embodiments, witness cameras 304 a-b can be fixed in eachangular position for the duration of a performance by actor 306, orwitness cameras 304 a-b can dynamically adjust its angular positionduring the performance so that central axes 604 a-b of witness cameras304 a-b are continuously aligned with actor 306 as actor 306 movesaround a set during the performance. In the latter case, one or moresensors and motors can be implemented to track the position of actor 306and mechanically rotate cameras 304 a-b in real time to align theircentral axes 604 a-b with actor 306.

II. Gel-Based Markers

As briefly mentioned above with respect to FIGS. 2 and 3, a plurality ofmarkers can be positioned on an actor's face to capture the motion of anactor's head by reflecting invisible light but not visible light.According to some embodiments of the present disclosure, the markers canbe retroreflective gel-based markers that can be applied to an actor'sface as if it were makeup. As a retroreflective substance, each marker,when applied to an actor's face, can act as a surface that reflectslight back to its source with a minimum of scattering along a vectorthat is parallel but opposite in direction from the light's source. Bybeing retroreflective, each marker can effectively negate any noise fromambient light. For instance, under normal lighting conditions indoors(i.e., absent lights directly beaming at the markers), the markers maynot be visible or have negligible visibility. For instances where a setis positioned outside, the sun can emit vast amounts of IR light.However, because the markers are retroreflective, the IR light emittedfrom the sun may not reflect back to the witness cameras. Instead, onlythe IR light emitted from the witness camera light sources (e.g., ringof IR LEDs around the witness cameras' lenses) will get reflected backto the witness cameras.

To enable the retroreflectivity of the gel-based markers, the gel-basedmarkers can be formed of a plurality of microspheres suspended within agel. The plurality of microspheres can be formed of glass or some othermirror-like material that enables the retroreflective properties of thegel-based markers. In some embodiments, the plurality of microspheresare formed of a first set of microspheres having a first diameter, and asecond set of microspheres having a second diameter different from thefirst. The first set of microspheres can have a larger diameter than thesecond set of microspheres so that the spaces between the first set ofmicrospheres can be filled in by the second set of microspheres toachieve a fuller coverage of a surface upon which the gel-based markeris applied. In some embodiments, the gel in which the microspheres aresuspended can be substantially transparent to IR light so that IR lightcan enter and exit the gel without being substantially attenuated. Insome embodiments, the gel is not transparent to visible light, buttransparent to IR light. In such cases, the gel can exhibit a pigmentthat matches the skin color of the actor so that the markers can beinconspicuous when worn by the actor. The gel may be any suitable typeof gel, such as standard hand sanitizer or a glycerin-based gel.

In some embodiments, the gel-based markers can be positioned at variouslocations on an actor's face to enable motion capture of the actor'sskull as he or she is performing. For example, the gel-based markers maybe applied to two, three, six, eight, or more points on an actor's face.The markers can be positioned on substantially rigid parts of an actor'sface to minimize distortion caused by facial movement during aperformance. FIG. 7 is a simplified illustration 700 of exemplarypositions for gel-based markers 702 a-g that enable motion capture ofthe skull of an actor 704 during a performance, according to someembodiments of the present disclosure. As shown in FIG. 7, markers 702 aand 702 e can be positioned at the temples of actor 704, markers 702 band 702 c can be positioned along the hairline of actor 704, markers 702f and 702 g can be positioned on the nose bridge and tip, respectively,and marker 702 h can be positioned on the chin of actor 704. Thesepositions are selected because they may be substantially free ofmovement caused by facial expressions and talking. That way, thepositions can closely track the movement of the skull of actor 704. Bytracking these positions, the witness cameras can more accuratelycapture the movement of the actor's head.

Each marker 702 a-h can be any shape suitable for motion capture bywitness cameras. For instance, each marker can be substantiallycircular, oval, triangular, square, rectangular, and the like. It is tobe appreciated that any shape that does not depart from the spirit andscope of the present disclosure can be utilized in embodiments herein.

According to some embodiments of the present disclosure, and asmentioned several times herein, markers 702 a-h can be unreflective andunabsorptive to visible light, but highly retroreflective to IR light.Thus, even though a taking camera and one or more witness cameras arefilming an actor with markers 702 a-h, only the witness cameras maycapture markers 702 a-h. By applying markers that are only visible towitness cameras and not a taking camera, embodiments enable thegeneration of content using a minimal number of performances by aperformer. More specifically, a performer only needs to perform a singleperformance in order (1) to generate images directly usable for an itemof content and/or driving a digital character in a virtual environmentand (2) for accurately determining the location of a digital charactermapped to the actor's head in a virtual environment.

III. Method for Motion Capture

FIG. 8 is a flow diagram of a method 800 for performing motion capturewith a motion capture system, according to some embodiments of thepresent disclosure. At block 802, light within a first wavelengthspectrum can be emitted towards a performance area. For example,standalone witness camera light sources (e.g., sources 310 a-c), orwitness light sources (e.g., sources 310 a-b) formed as part ofrespective witness cameras mounted on a movable rig can emit invisiblelight towards an actor (e.g., actor 306 or 306) in a set, as discussedherein with respect to FIGS. 2 and 3. The invisible light can be withinthe IR light wavelength spectrum, such as within a wavelength spectrumof between 701 nm and 1 mm.

At block 804, a first plurality of images of a performance can becaptured by a first set of one or more cameras. As an example, images ofa plurality of markers applied to substantially rigid portions anactor's face (e.g., forehead, nose, cheek bones, temple, chin, etc.)while the actor is performing can be captured by witness cameras, e.g.,witness cameras 304 a-d or witness cameras 304 a-b in FIGS. 2 and 3 cancapture markers applied to the faces of actors 306 and 306,respectively.

At block 806, locations of at least one marker applied to the actor'sface can be identified. For instance, positions captured by witnesscameras 304 a-b can be triangulated to determine the locations of themarkers in the performance area. This location can then be used toposition a digital character, or one or more features thereof such asthe face of a digital character, whose position accurately correspondsto the location of the markers applied to the actor's face so that thedigital character can accurately represent the actor's face.

At block 808, position and motion data for a digital character in avirtual environment can be determined based on the identified locationsof the markers applied to the actor's face. For instance, a computersystem, e.g., computer system 122 in FIG. 1, can receive the capturedimages of one or more witness cameras and utilize the captured images todetermine the position of the markers on the actor via triangulation.Once the position of the markers are determined, then a digitalcharacter can be rendered and positioned at a location within thevirtual environment that corresponds to the determined positions of themarkers. In some embodiments, the position of the markers with respectto one another can be used to determine the orientation at which thedigital character faces in the virtual environment. For instance, theposition of the marker at the tip of the nose relative to the positionsof the markers at the temple, hairline, and chin can be used todetermine which way the actor's face is oriented. This information canthen be used to determine the orientation of the digital character inthe virtual environment.

At block 810, a second plurality of images of the performance can becaptured by a second set of one or more cameras. For instance, a takingcamera, e.g., taking camera 302 or 302 in FIGS. 2 and 3, respectively,can capture images of an actor and his or her surroundings in a setduring the actor's performance. In some embodiments, the second set ofone or more cameras captures the images simultaneously with the firstset of one or more cameras. That way, the captured images can be of thesame performance but just from different perspectives. However, thesecond plurality of images may be based upon what is perceived fromreflected visible light. For example, the way the actor's face andcostume looks, the way the chair looks, and how the actor is positionedwith respect to the chair can all be captured by the second set of oneor more cameras.

Thereafter, at block 812, content can be generated based on thedetermined positions for the digital character and the second pluralityof images. That is, content can be generated where the digital characteris positioned within the set as perceived by the taking camera. In someinstances, the digital character can be positioned where the actor ispositioned when viewed from the taking camera. Thus, the digitalcharacter can be have a size and positioning that accurately correspondsto the size and movements of the actor as captured by the witnesscameras when the witness cameras are capturing the images of the markerson the actor's face.

For example, 3D positioning of the markers can be determined viatriangulation techniques to determine the position of one or moremarkers on the surfaces of the actor's face. This process may beperformed at different times, to thereby determine where and how amarker on the face of an actor moves as he or she performs. The 3Dpositioning data may then be used to set a pose of the rigid portions ofa computer generated object, e.g. face. The computer generated objectcan be positioned within a setting captured in the second plurality ofimages by the second set of cameras. The second plurality of images maybe used by a suitable solver system to determine the movement of thosefeatures of the computer generated object that are substantiallynon-rigid (e.g., an actor's eyebrows, eyes, cheeks, etc). Since imagesof the markers and images of the actor during the performance werecaptured, the computer generated object can accurately be mapped to theactor's face in the resulting content.

IV. Example Computer System

FIG. 9 is a simplified block diagram of system 900 for creating computergraphics imagery (CGI) and computer-aided visual effects that mayimplement or incorporate various embodiments in accordance with thedisclosure. In this example, system 900 can include one or more designcomputers 910, object library 920, one or more object modeler systems930, one or more object articulation systems 940, one or more objectvisual effects systems 950, one or more object simulation systems 960,and one or more object rendering systems 970. Any of the systems 930-970may be invoked by or used directly by a user of the one or more designcomputers 910 and/or automatically invoked by or used by one or moreprocesses associated with the one or more design computers 910. Any ofthe elements of system 900 can include hardware and/or software elementsconfigured for specific functions.

The one or more design computers 910 can include hardware and softwareelements configured for designing CGI and assisting with computer-aidedanimation. Each of the one or more design computers 910 may be embodiedas a single computing device or a set of one or more computing devices.Some examples of computing devices are PCs, laptops, workstations,mainframes, cluster computing system, grid computing systems, cloudcomputing systems, embedded devices, computer graphics devices, gamingdevices and consoles, consumer electronic devices having programmableprocessors, or the like. The one or more design computers 910 may beused at various stages of a production process (e.g., pre-production,designing, creating, editing, simulating, animating, rendering,post-production, etc.) to produce images, image sequences, motionpictures, video, audio, or associated effects related to CGI andanimation.

In one example, a user of the one or more design computers 910 acting asa modeler may employ one or more systems or tools to design, create, ormodify objects within a computer-generated scene. The modeler may usemodeling software to sculpt and refine a 3D model to fit predefinedaesthetic needs of one or more character designers. The modeler maydesign and maintain a modeling topology conducive to a storyboardedrange of deformations. In another example, a user of the one or moredesign computers 910 acting as an articulator may employ one or moresystems or tools to design, create, or modify controls or animationvariables (avars) of models. In general, rigging is a process of givingan object, such as a character model, controls for movement, therein“articulating” its ranges of motion. The articulator may work closelywith one or more animators in rig building to provide and refine anarticulation of the full range of expressions and body movement neededto support a character's acting range in an animation. In a furtherexample, a user of design computer 910 acting as an animator may employone or more systems or tools to specify motion and position of one ormore objects over time to produce an animation.

Object library 920 can include elements configured for storing andaccessing information related to objects used by the one or more designcomputers 910 during the various stages of a production process toproduce CGI and animation. Some examples of object library 920 caninclude a file, a database, or other storage devices and mechanisms.Object library 920 may be locally accessible to the one or more designcomputers 910 or hosted by one or more external computer systems.

Some examples of information stored in object library 920 can include anobject itself, metadata, object geometry, object topology, rigging,control data, animation data, animation cues, simulation data, texturedata, lighting data, shader code, or the like. An object stored inobject library 920 can include any entity that has an n-dimensional(e.g., 2D or 3D) surface geometry. The shape of the object can include aset of points or locations in space (e.g., object space) that make upthe object's surface. Topology of an object can include the connectivityof the surface of the object (e.g., the genus or number of holes in anobject) or the vertex/edge/face connectivity of an object.

The one or more object modeling systems 930 can include hardware and/orsoftware elements configured for modeling one or more objects. Modelingcan include the creating, sculpting, and editing of an object. Invarious embodiments, the one or more object modeling systems 930 may beconfigured to generated a model to include a description of the shape ofan object. The one or more object modeling systems 930 can be configuredto facilitate the creation and/or editing of features, such asnon-uniform rational B-splines or NURBS, polygons and subdivisionsurfaces (or SubDivs), that may be used to describe the shape of anobject. In general, polygons are a widely used model medium due to theirrelative stability and functionality. Polygons can also act as thebridge between NURBS and SubDivs. NURBS are used mainly for theirready-smooth appearance and generally respond well to deformations.SubDivs are a combination of both NURBS and polygons representing asmooth surface via the specification of a coarser piecewise linearpolygon mesh. A single object may have several different models thatdescribe its shape.

The one or more object modeling systems 930 may further generate modeldata (e.g., 2D and 3D model data) for use by other elements of system900 or that can be stored in object library 920. The one or more objectmodeling systems 930 may be configured to allow a user to associateadditional information, metadata, color, lighting, rigging, controls, orthe like, with all or a portion of the generated model data.

The one or more object articulation systems 940 can include hardwareand/or software elements configured to articulating one or morecomputer-generated objects. Articulation can include the building orcreation of rigs, the rigging of an object, and the editing of rigging.In various embodiments, the one or more articulation systems 940 can beconfigured to enable the specification of rigging for an object, such asfor internal skeletal structures or eternal features, and to define howinput motion deforms the object. One technique is called “skeletalanimation,” in which a character can be represented in at least twoparts: a surface representation used to draw the character (called theskin) and a hierarchical set of bones used for animation (called theskeleton).

The one or more object articulation systems 940 may further generatearticulation data (e.g., data associated with controls or animationsvariables) for use by other elements of system 900 or that can be storedin object library 920. The one or more object articulation systems 940may be configured to allow a user to associate additional information,metadata, color, lighting, rigging, controls, or the like, with all or aportion of the generated articulation data.

The one or more object visual effects systems 950 can include hardwareand/or software elements configured for animating one or morecomputer-generated objects. Animation can include the specification ofmotion and position of an object over time. The one or more objectvisual effects systems 950 may be invoked by or used directly by a userof the one or more design computers 910 and/or automatically invoked byor used by one or more processes associated with the one or more designcomputers 910.

In various embodiments, the one or more visual effects systems 950 maybe configured to enable users to manipulate controls or animationvariables or utilized character rigging to specify one or more keyframes of animation sequence. The one or more visual effects systems 950generate intermediary frames based on the one or more key frames. Insome embodiments, the one or more visual effects systems 950 may beconfigured to enable users to specify animation cues, paths, or the likeaccording to one or more predefined sequences. The one or more visualeffects systems 950 generate frames of the animation based on theanimation cues or paths. In further embodiments, the one or more visualeffects systems 950 may be configured to enable users to defineanimations using one or more animation languages, morphs, deformations,or the like. In various embodiments, the one or more visual effectssystems 950 may be configured to generate animated content utilizingcaptured images from taking and witness cameras of any of the motioncapture systems discussed herein.

The one or more object visual effects systems 950 may further generateanimation data (e.g., inputs associated with controls or animationsvariables) for use by other elements of system 900 or that can be storedin object library 920. The one or more object visual effects systems 950may be configured to allow a user to associate additional information,metadata, color, lighting, rigging, controls, or the like, with all or aportion of the generated animation data.

The one or more object simulation systems 960 can include hardwareand/or software elements configured for simulating one or morecomputer-generated objects. Simulation can include determining motionand position of an object over time in response to one or more simulatedforces or conditions. The one or more object simulation systems 960 maybe invoked by or used directly by a user of the one or more designcomputers 910 and/or automatically invoked by or used by one or moreprocesses associated with the one or more design computers 910.

In various embodiments, the one or more object simulation systems 960may be configured to enables users to create, define, or edit simulationengines, such as a physics engine or physics processing unit (PPU/GPGPU)using one or more physically-based numerical techniques. In general, aphysics engine can include a computer program that simulates one or morephysics models (e.g., a Newtonian physics model), using variables suchas mass, velocity, friction, wind resistance, or the like. The physicsengine may simulate and predict effects under different conditions thatwould approximate what happens to an object according to the physicsmodel. The one or more object simulation systems 960 may be used tosimulate the behavior of objects, such as hair, fur, and cloth, inresponse to a physics model and/or animation of one or more charactersand objects within a computer-generated scene.

The one or more object simulation systems 960 may further generatesimulation data (e.g., motion and position of an object over time) foruse by other elements of system 90 or that can be stored in objectlibrary 920. The generated simulation data may be combined with or usedin addition to animation data generated by the one or more object visualeffects systems 950. The one or more object simulation systems 960 maybe configured to allow a user to associate additional information,metadata, color, lighting, rigging, controls, or the like, with all or aportion of the generated simulation data.

The one or more object rendering systems 970 can include hardware and/orsoftware element configured for “rendering” or generating one or moreimages of one or more computer-generated objects. “Rendering” caninclude generating an image from a model based on information such asgeometry, viewpoint, texture, lighting, and shading information. The oneor more object rendering systems 970 may be invoked by or used directlyby a user of the one or more design computers 910 and/or automaticallyinvoked by or used by one or more processes associated with the one ormore design computers 910. One example of a software program embodied asthe one or more object rendering systems 970 can include PhotoRealisticRenderMan, or PRMan, produced by Pixar Animations Studios of Emeryville,Calif.

In various embodiments, the one or more object rendering systems 970 canbe configured to render one or more objects to produce one or morecomputer-generated images or a set of images over time that provide ananimation. The one or more object rendering systems 970 may generatedigital images or raster graphics images.

In various embodiments, a rendered image can be understood in terms of anumber of visible features. Some examples of visible features that maybe considered by the one or more object rendering systems 970 mayinclude shading (e.g., techniques relating to how the color andbrightness of a surface varies with lighting), texture-mapping (e.g.,techniques relating to applying detail information to surfaces orobjects using maps), bump-mapping (e.g., techniques relating tosimulating small-scale bumpiness on surfaces), fogging/participatingmedium (e.g., techniques relating to how light dims when passing throughnon-clear atmosphere or air) shadows (e.g., techniques relating toeffects of obstructing light), soft shadows (e.g., techniques relatingto varying darkness caused by partially obscured light sources),reflection (e.g., techniques relating to mirror-like or highly glossyreflection), transparency or opacity (e.g., techniques relating to sharptransmissions of light through solid objects), translucency (e.g.,techniques relating to highly scattered transmissions of light throughsolid objects), refraction (e.g., techniques relating to bending oflight associated with transparency), diffraction (e.g., techniquesrelating to bending, spreading and interference of light passing by anobject or aperture that disrupts the ray), indirect illumination (e.g.,techniques relating to surfaces illuminated by light reflected off othersurfaces, rather than directly from a light source, also known as globalillumination), caustics (e.g., a form of indirect illumination withtechniques relating to reflections of light off a shiny object, orfocusing of light through a transparent object, to produce brighthighlight rays on another object), depth of field (e.g., techniquesrelating to how objects appear blurry or out of focus when too far infront of or behind the object in focus), motion blur (e.g., techniquesrelating to how objects appear blurry due to high-speed motion, or themotion of the camera), non-photorealistic rendering (e.g., techniquesrelating to rendering of scenes in an artistic style, intended to looklike a painting or drawing), or the like.

The one or more object rendering systems 970 may further render images(e.g., motion and position of an object over time) for use by otherelements of system 900 or that can be stored in object library 920. Theone or more object rendering systems 970 may be configured to allow auser to associate additional information or metadata with all or aportion of the rendered image.

FIG. 10 is a block diagram of computer system 1000. FIG. 10 is merelyillustrative. In some embodiments, a computer system includes a singlecomputer apparatus, where the subsystems can be the components of thecomputer apparatus. In other embodiments, a computer system can includemultiple computer apparatuses, each being a subsystem, with internalcomponents. Computer system 1000 and any of its components or subsystemscan include hardware and/or software elements configured for performingmethods described herein.

Computer system 1000 may include familiar computer components, such asone or more one or more data processors or central processing units(CPUs) 1005, one or more graphics processors or graphical processingunits (GPUs) 1010, memory subsystem 1015, storage subsystem 1020, one ormore input/output (I/O) interfaces 1025, communications interface 1030,or the like. Computer system 1000 can include system bus 1035interconnecting the above components and providing functionality, suchconnectivity and inter-device communication.

The one or more data processors or central processing units (CPUs) 1005can execute logic or program code or for providing application-specificfunctionality. Some examples of CPU(s) 1005 can include one or moremicroprocessors (e.g., single core and multi-core) or micro-controllers,one or more field-gate programmable arrays (FPGAs), andapplication-specific integrated circuits (ASICs). As used herein, aprocessor includes a multi-core processor on a same integrated chip, ormultiple processing units on a single circuit board or networked.

The one or more graphics processor or graphical processing units (GPUs)1010 can execute logic or program code associated with graphics or forproviding graphics-specific functionality. GPUs 1010 may include anyconventional graphics processing unit, such as those provided byconventional video cards. In various embodiments, GPUs 1010 may includeone or more vector or parallel processing units. These GPUs may be userprogrammable, and include hardware elements for encoding/decodingspecific types of data (e.g., video data) or for accelerating 2D or 3Ddrawing operations, texturing operations, shading operations, or thelike. The one or more graphics processors or graphical processing units(GPUs) 1010 may include any number of registers, logic units, arithmeticunits, caches, memory interfaces, or the like.

Memory subsystem 1015 can store information, e.g., usingmachine-readable articles, information storage devices, orcomputer-readable storage media. Some examples can include random accessmemories (RAM), read-only-memories (ROMS), volatile memories,non-volatile memories, and other semiconductor memories. Memorysubsystem 1015 can include data and program code 1040.

Storage subsystem 1020 can also store information using machine-readablearticles, information storage devices, or computer-readable storagemedia. Storage subsystem 1020 may store information using storage media1045. Some examples of storage media 1045 used by storage subsystem 1020can include floppy disks, hard disks, optical storage media such asCD-ROMS, DVDs and bar codes, removable storage devices, networkedstorage devices, or the like. In some embodiments, all or part of dataand program code 1040 may be stored using storage subsystem 1020.

The one or more input/output (I/O) interfaces 1025 can perform I/Ooperations. One or more input devices 1050 and/or one or more outputdevices 1055 may be communicatively coupled to the one or more I/Ointerfaces 1025. The one or more input devices 1050 can receiveinformation from one or more sources for computer system 1000. Someexamples of the one or more input devices 1050 may include a computermouse, a trackball, a track pad, a joystick, a wireless remote, adrawing tablet, a voice command system, an eye tracking system, externalstorage systems, a monitor appropriately configured as a touch screen, acommunications interface appropriately configured as a transceiver, orthe like. In various embodiments, the one or more input devices 1050 mayallow a user of computer system 1000 to interact with one or morenon-graphical or graphical user interfaces to enter a comment, selectobjects, icons, text, user interface widgets, or other user interfaceelements that appear on a monitor/display device via a command, a clickof a button, or the like.

The one or more output devices 1055 can output information to one ormore destinations for computer system 1000. Some examples of the one ormore output devices 1055 can include a printer, a fax, a feedback devicefor a mouse or joystick, external storage systems, a monitor or otherdisplay device, a communications interface appropriately configured as atransceiver, or the like. The one or more output devices 1055 may allowa user of computer system 1000 to view objects, icons, text, userinterface widgets, or other user interface elements. A display device ormonitor may be used with computer system 1000 and can include hardwareand/or software elements configured for displaying information.

Communications interface 1030 can perform communications operations,including sending and receiving data. Some examples of communicationsinterface 1030 may include a network communications interface (e.g.Ethernet, Wi-Fi, etc.). For example, communications interface 1030 maybe coupled to communications network/external bus 1051, such as acomputer network, a USB hub, or the like. A computer system can includea plurality of the same components or subsystems, e.g., connectedtogether by communications interface 1030 or by an internal interface.In some embodiments, computer systems, subsystem, or apparatuses cancommunicate over a network. In such instances, one computer can beconsidered a client and another computer a server, where each can bepart of a same computer system. A client and a server can each includemultiple systems, subsystems, or components.

Computer system 1000 may also include one or more applications (e.g.,software components or functions) to be executed by a processor toexecute, perform, or otherwise implement techniques disclosed herein.These applications may be embodied as data and program code 1040.Additionally, computer programs, executable computer code,human-readable source code, shader code, rendering engines, or the like,and data, such as image files, models including geometrical descriptionsof objects, ordered geometric descriptions of objects, proceduraldescriptions of models, scene descriptor files, or the like, may bestored in memory subsystem 1015 and/or storage subsystem 1020.

Such programs may also be encoded and transmitted using carrier signalsadapted for transmission via wired, optical, and/or wireless networksconforming to a variety of protocols, including the Internet. As such, acomputer readable medium according to an embodiment of the presentinvention may be created using a data signal encoded with such programs.Computer readable media encoded with the program code may be packagedwith a compatible device or provided separately from other devices(e.g., via Internet download). Any such computer readable medium mayreside on or within a single computer product (e.g. a hard drive, a CD,or an entire computer system), and may be present on or within differentcomputer products within a system or network. A computer system mayinclude a monitor, printer, or other suitable display for providing anyof the results mentioned herein to a user.

Any of the methods described herein may be totally or partiallyperformed with a computer system including one or more processors, whichcan be configured to perform the steps. Thus, embodiments can bedirected to computer systems configured to perform the steps of any ofthe methods described herein, potentially with different componentsperforming a respective steps or a respective group of steps. Althoughpresented as numbered steps, steps of methods herein can be performed ata same time or in a different order. Additionally, portions of thesesteps may be used with portions of other steps from other methods. Also,all or portions of a step may be optional. Additionally, any of thesteps of any of the methods can be performed with modules, circuits, orother means for performing these steps.

In the foregoing specification, aspects of the invention are describedwith reference to specific embodiments thereof, but those skilled in theart will recognize that the invention is not limited thereto. Variousfeatures and aspects of the above-described invention may be usedindividually or jointly. Further, embodiments can be utilized in anynumber of environments and applications beyond those described hereinwithout departing from the broader spirit and scope of thespecification. The specification and drawings are, accordingly, to beregarded as illustrative rather than restrictive.

Additionally, for the purposes of explanation, numerous specific detailshave been set forth in order to provide a thorough understanding ofvarious embodiments of the present invention. It will be apparent,however, to one skilled in the art that embodiments of the presentinvention may be practiced without some of these specific details. Inother instances, well-known structures and devices may have been shownin block diagram form.

This description has provided exemplary embodiments only, and is notintended to limit the scope, applicability, or configuration of thedisclosure. Rather, this description of the exemplary embodimentsprovides those skilled in the art with an enabling description forimplementing an exemplary embodiment. It should be understood thatvarious changes may be made in the function and arrangement of elementswithout departing from the spirit and scope of the invention as setforth in the appended claims.

Specific details have been given in the description to provide athorough understanding of the embodiments. However, it will beunderstood by one of ordinary skill in the art that the embodiments maybe practiced without these specific details. For example, circuits,systems, networks, processes, and other components may be shown ascomponents in block diagram form in order not to obscure the embodimentsin unnecessary detail. In other instances, well-known circuits,processes, algorithms, structures, and techniques may be shown withoutunnecessary detail in order to avoid obscuring the embodiments.

Also, it is noted that individual embodiments may be described as aprocess which is depicted as a flowchart, a flow diagram, a data flowdiagram, a structure diagram, or a block diagram. Although a flowchartmay describe the operations as a sequential process, many of theoperations can be performed in parallel or concurrently. In addition,the order of the operations may be re-arranged. A process is terminatedwhen its operations are completed, but could have additional steps notincluded in a figure. A process may correspond to a method, a function,a procedure, a subroutine, a subprogram, etc. When a process correspondsto a function, its termination can correspond to a return of thefunction to the calling function or the main function.

The term “non-transitory, computer-readable medium” includes, but is notlimited to portable or fixed storage devices, optical storage devices,and various other mediums capable of storing instruction(s) and/or data.A code segment or machine-executable instructions may represent aprocedure, a function, a subprogram, a program, a routine, a subroutine,a module, a software package, a class, or any combination ofinstructions, data structures, or program statements. A code segment maybe coupled to another code segment or a hardware circuit by passingand/or receiving information, data, arguments, parameters, or memorycontents. Information, arguments, parameters, data, etc., may be passed,forwarded, or transmitted via any suitable means including memorysharing, message passing, token passing, network transmission, etc.

Furthermore, embodiments may be implemented by hardware, software,firmware, middleware, microcode, hardware description languages, or anycombination thereof. When implemented in software, firmware, middlewareor microcode, the program code or code segments to perform the necessarytasks may be stored in a machine readable medium. A processor(s) mayperform the necessary tasks.

Additionally, for the purposes of illustration, methods may have beendescribed in a particular order. It should be appreciated that inalternate embodiments, the methods may be performed in a different orderthan that described. It should also be appreciated that the methodsdescribed above may be performed by hardware components or may beembodied in sequences of machine-executable instructions, which may beused to cause a machine, such as a general-purpose or special-purposeprocessor or logic circuits programmed with the instructions to performthe methods. These machine-executable instructions may be stored on oneor more machine readable mediums, such as CD-ROMs or other type ofoptical disks, floppy diskettes, ROMs, RAMs, EPROMs, EEPROMs, magneticor optical cards, flash memory, or other types of machine-readablemediums suitable for storing electronic instructions. Alternatively, themethods may be performed by a combination of hardware and software.

Although the disclosure has been described with respect to specificembodiments, it will be appreciated that the disclosure is intended tocover all modifications and equivalents within the scope of thefollowing claims.

What is claimed is:
 1. A computer-implemented method of capturing motionwith a motion capture system, the method comprising: emitting firstlight at wavelengths within a first spectrum towards an actor in aperformance area; capturing a first plurality of images of a performanceusing a first set of one or more cameras operable to capture the firstlight at wavelengths in the first spectrum, the first plurality ofimages representing captured emitted first light that has been reflectedoff of at least one marker applied to a face of the actor, wherein thefirst plurality of images is captured by two witness cameras of thefirst set of one or more cameras laterally positioned on opposite sidesof a taking camera of a second set of one or more cameras attached to amoveable rig; identifying locations of at least one marker applied tothe face of the actor by analyzing at least some of the first pluralityof images captured by at least one camera from the first set of one ormore cameras; generating position and motion data for a digitalcharacter based on the identified locations of the at least one markerapplied to the face of the actor, wherein the at least one marker is agel-based marker that reflects the first light at wavelengths in thefirst spectrum that is substantially invisible to a human eye and isdetected by at least one camera of the first set of the one or morecameras; capturing a second plurality of images of the performance usinga second set of one or more cameras operable to capture second light atwavelengths in a second spectrum different from the first spectrum, thesecond plurality of images representing at least a portion of a body ofthe actor and the performance area; and generating content based on thegenerated position and motion data for the digital character and thesecond plurality of images.
 2. The computer-implemented method of claim1, wherein the at least one marker does not reflect the second light atwavelengths in the second spectrum.
 3. The computer-implemented methodof claim 1, wherein the first plurality of images and the secondplurality of images are simultaneously captured by the respective firstset of one or more cameras and the second set of one or more cameras. 4.The computer-implemented method of claim 1, wherein the first pluralityof images are captured by receiving the reflected emitted first lightpropagating along a vector that is parallel but opposite in directionfrom a light source emitting the first light.
 5. Thecomputer-implemented method of claim 4, wherein the first light isemitted from at least one light source configured as a ring of lightspositioned around a lens of a respective camera of the first set of oneor more cameras.
 6. The computer-implemented method of claim 5, whereinthe first plurality of images is captured by two witness cameras of thefirst set of one or more cameras laterally positioned on opposite sidesof a taking camera of the second set of one or more cameras.
 7. Thecomputer-implemented method of claim 6, wherein the second plurality ofimages is captured by the taking camera.
 8. The computer-implementedmethod of claim 1, wherein the first spectrum is a spectrum of lightthat is visible to a naked human eye, and the second spectrum is aspectrum of light that is substantially invisible to the naked humaneye.
 9. The computer-implemented method of claim 8, wherein the secondspectrum is defined by the spectrum of infrared light having wavelengthsbetween 701 nm to 1 mm.
 10. A computer product comprising anon-transitory computer readable medium storing instructions that whenexecuted control a device including one or more processors, theinstructions comprising: emitting light at wavelengths within a firstspectrum towards an actor in a performance area; capturing a firstplurality of images of a performance using a first set of one or morecameras operable to capture first light at wavelengths in the firstspectrum, the first plurality of images representing captured emittedfirst light that has been reflected off of at least one marker appliedto a face of the actor, wherein the first plurality of images iscaptured by two witness cameras of the first set of one or more cameraslaterally positioned on opposite sides of a taking camera of a secondset of one or more cameras attached to a moveable rig; identifyinglocations of at least one marker applied to the face of the actor byanalyzing at least some of the first plurality of images captured by atleast one camera from the first set of one or more cameras; generatingposition and motion data for a digital character based on the identifiedlocations of the at least one marker applied to the face of the actor,wherein the at least one marker is a gel-based marker that reflects thefirst light at wavelengths in the first spectrum that is substantiallyinvisible to a human eye and is detected by at least one camera of thefirst set of the one or more cameras; capturing a second plurality ofimages of the performance using a second set of one or more camerasoperable to capture second light at wavelengths in a second spectrumdifferent from the first spectrum, the second plurality of imagesrepresenting at least a portion of a body of the actor and theperformance area; and generating content based on the generated positionand motion data for the digital character and the second plurality ofimages.
 11. The computer product of claim 10, wherein the at least onemarker does not reflect the second light at wavelengths in the secondspectrum.
 12. The computer product of claim 10, wherein the firstplurality of images and the second plurality of images aresimultaneously captured by the respective first set of one or morecameras and the second set of one or more cameras.
 13. The computerproduct of claim 10, wherein first plurality of images are captured byreceiving the reflected emitted first light propagating along a vectorthat is parallel but opposite in direction from a light source emittingthe first light.
 14. The computer product of claim 10, wherein the firstspectrum is a spectrum of light that is visible to a naked human eye,and the second spectrum is a spectrum of light that is substantiallyinvisible to the naked human eye.
 15. The computer product of claim 14,wherein the first light is emitted from at least one light sourceconfigured as a ring of lights positioned around a lens of a respectivecamera of the first set of one or more cameras.
 16. A computer systemfor a motion capture system, the computer system comprising: one or moreprocessors; and memory containing code for instructing the one or moreprocessors to: emit light at wavelengths within a first spectrum towardsan actor in a performance area; capture a first plurality of images of aperformance using a first set of one or more cameras operable to capturelight at wavelengths in the first spectrum, the first plurality ofimages representing captured emitted light that has been reflected offof at least one marker applied to a face of the actor, wherein the firstplurality of images is captured by two witness cameras of the first setof one or more cameras laterally positioned on opposite sides of ataking camera of a second set of one or more cameras attached to amoveable rig; identify locations of at least one marker applied to theface of the actor by analyzing at least some of the first plurality ofimages captured by at least one camera from the first set of one or morecameras; generate position and motion data for a digital character basedon the identified locations of the at least one marker applied to theface of the actor, wherein the at least one marker is a gel-based markerthat reflects the first light at wavelengths in the first spectrum thatis substantially invisible to a human eye and is detected by at leastone camera of the first set of the one or more cameras; capture a secondplurality of images of the performance using a second set of one or morecameras operable to capture light at wavelengths in a second spectrumdifferent from the first spectrum, the second plurality of imagesrepresenting at least a portion of a body of the actor and theperformance area; and generate content based on the generated positionand motion data for the digital character and the second plurality ofimages.
 17. The computer system of claim 16, wherein the at least onemarker does not reflect the second light at wavelengths in the secondspectrum.
 18. The computer system of claim 16, wherein the firstplurality of images and the second plurality of images aresimultaneously captured by the respective first set of one or morecameras and the second set of one or more cameras.
 19. The computersystem of claim 16, wherein first plurality of images are captured byreceiving the reflected emitted light propagating along a vector that isparallel but opposite in direction from a light source emitting thelight.
 20. The computer system of claim 16, wherein the first spectrumis a spectrum of light that is visible to a naked human eye, and thesecond spectrum is a spectrum of light that is substantially invisibleto the naked human eye.